4,4-Dimethyl-3,5-bis(4'-fluorophenyl)-4H-pyrazole | 155886-81-0

• 分子结构分类: 有机化合物 - 苯类化合物 - 苯和取代衍生物
• 英文名称: 4,4-Dimethyl-3,5-bis(4'-fluorophenyl)-4H-pyrazole
• 英文别名: 3,5-Bis(4-fluorophenyl)-4,4-dimethylpyrazole
• CAS: 155886-81-0
• 化学式: C₁₇H₁₄F₂N₂
• 分子量: 284.308
• InChiKey: IIFTZBBEWUKFHD-UHFFFAOYSA-N

计算性质

• 辛醇/水分配系数(LogP)：
  4.6
• 重原子数：
  21
• 可旋转键数：
  2
• 环数：
  3.0
• sp3杂化的碳原子比例：
  0.18
• 拓扑面积：
  24.7
• 氢给体数：
  0
• 氢受体数：
  4

反应信息

• 作为反应物：
  描述：

  4,4-Dimethyl-3,5-bis(4'-fluorophenyl)-4H-pyrazole 在 三氟乙酸 作用下， 以 二氯甲烷 、 氘代苯 为溶剂， 反应 0.17h， 生成 3,3-Dimethyl-2,4-bis(4'-fluorophenyl)-endo-tricyclo<3.3.0.0^2,4>oct-6-ene
  参考文献：
  名称：

  Electronic Substituent Effects on the Acid-Catalyzed [4+ + 2] Cycloaddition of Isopyrazoles with Cyclopentadiene and the Photochemical and Thermal Denitrogenation of the Resulting 1,4-Diaryl-7,7-dimethyl-2,3-diazabicyclo[2.2.1]hept-2-ene Azoalkanes to Bicyclo[2.1.0]pentanes

  摘要：

  Eight symmetrically disubstituted 3,5-diaryl-4,4-dimethylisopyrazoles 6 with para and meta substituents (OMe, Me, H, F, Cl, Br, CN, NO2) and two unsymmetrically para-substituted derivatives (OMe and NO2; Me and CO(2)Me) were synthesized from the corresponding 1,3-diaryl-2,2-dimethyl-1,3-propanediones 5, which in turn were readily available by 2,2-dimethylation of the diones 4. The acid-catalyzed cycloaddition of cyclopentadiene to the isopyrazoles 6, a Diels-Alder reaction with inverse electron demand, afforded the 1,4-diaryl-substituted gem-dimethyl azoalkanes 7 of the diazabicyco[2.2.1]hept-2-ene (DBH) type. The cycloadduct yields were strongly dependent on the nature of the aryl substituents and highest for the electron-withdrawing substituents. In acidic solution, the azoalkanes showed cycloreversion to generate an equilibrium between isopyrazole 6, cyclopentadiene, and azoalkane 7. For the p-methoxy derivative, cycloreversion was essentially quantitative, whereas only 20% cycloreversion occurred for the para nitro compound. A positive Hammett rho value (rho = 3.24 for 2 equiv of CF3COOH) was determined for the equilibrium constants of the acid-catalyzed [4(+) + 2] cycloaddition. The unsymmetrically substituted isopyrazoles gave two regioisomeric cycloadducts with a slight excess of one isomer. The direct and triplet-sensitized photochemical and thermal denitrogenation of the azoalkanes 7 gave in quantitative yields the 1,4-diaryl-substituted bicyclo[2.1.0]pentanes (BCP) 8 with retention of configuration. The azoalkanes 7 and the housanes 8 are more persistent than the related 1,4-diaryl-substituted DBH and BCP derivatives. The stabilizing effect is rationalized in terms of less favorable benzylic conjugation in the transition states for C-N (azoalkanes) and C-C (housanes) bond cleavage due to steric interactions between the geminal methyl groups at the methane bridge and the diaryl substituents at the bridgehead sites.

  DOI：

  10.1021/jo00093a010
• 作为产物：
  描述：

  2,2-Dimethyl-1,3-bis(4'-fluorophenyl)-1,3-propanedione 在 一水合肼 作用下， 以 氯仿 为溶剂， 反应 6.0h， 以80%的产率得到4,4-Dimethyl-3,5-bis(4'-fluorophenyl)-4H-pyrazole
  参考文献：
  名称：

  Electronic Substituent Effects on the Acid-Catalyzed [4+ + 2] Cycloaddition of Isopyrazoles with Cyclopentadiene and the Photochemical and Thermal Denitrogenation of the Resulting 1,4-Diaryl-7,7-dimethyl-2,3-diazabicyclo[2.2.1]hept-2-ene Azoalkanes to Bicyclo[2.1.0]pentanes

  摘要：

  Eight symmetrically disubstituted 3,5-diaryl-4,4-dimethylisopyrazoles 6 with para and meta substituents (OMe, Me, H, F, Cl, Br, CN, NO2) and two unsymmetrically para-substituted derivatives (OMe and NO2; Me and CO(2)Me) were synthesized from the corresponding 1,3-diaryl-2,2-dimethyl-1,3-propanediones 5, which in turn were readily available by 2,2-dimethylation of the diones 4. The acid-catalyzed cycloaddition of cyclopentadiene to the isopyrazoles 6, a Diels-Alder reaction with inverse electron demand, afforded the 1,4-diaryl-substituted gem-dimethyl azoalkanes 7 of the diazabicyco[2.2.1]hept-2-ene (DBH) type. The cycloadduct yields were strongly dependent on the nature of the aryl substituents and highest for the electron-withdrawing substituents. In acidic solution, the azoalkanes showed cycloreversion to generate an equilibrium between isopyrazole 6, cyclopentadiene, and azoalkane 7. For the p-methoxy derivative, cycloreversion was essentially quantitative, whereas only 20% cycloreversion occurred for the para nitro compound. A positive Hammett rho value (rho = 3.24 for 2 equiv of CF3COOH) was determined for the equilibrium constants of the acid-catalyzed [4(+) + 2] cycloaddition. The unsymmetrically substituted isopyrazoles gave two regioisomeric cycloadducts with a slight excess of one isomer. The direct and triplet-sensitized photochemical and thermal denitrogenation of the azoalkanes 7 gave in quantitative yields the 1,4-diaryl-substituted bicyclo[2.1.0]pentanes (BCP) 8 with retention of configuration. The azoalkanes 7 and the housanes 8 are more persistent than the related 1,4-diaryl-substituted DBH and BCP derivatives. The stabilizing effect is rationalized in terms of less favorable benzylic conjugation in the transition states for C-N (azoalkanes) and C-C (housanes) bond cleavage due to steric interactions between the geminal methyl groups at the methane bridge and the diaryl substituents at the bridgehead sites.

  DOI：

  10.1021/jo00093a010

文献信息

• Electronic Substituent Effects on the Acid-Catalyzed [4+ + 2] Cycloaddition of Isopyrazoles with Cyclopentadiene and the Photochemical and Thermal Denitrogenation of the Resulting 1,4-Diaryl-7,7-dimethyl-2,3-diazabicyclo[2.2.1]hept-2-ene Azoalkanes to Bicyclo[2.1.0]pentanes
  作者：Waldemar Adam、Heinrich M. Harrer、Werner M. Nau、Karl Peters

  DOI：10.1021/jo00093a010

  日期：1994.7

  Eight symmetrically disubstituted 3,5-diaryl-4,4-dimethylisopyrazoles 6 with para and meta substituents (OMe, Me, H, F, Cl, Br, CN, NO2) and two unsymmetrically para-substituted derivatives (OMe and NO2; Me and CO(2)Me) were synthesized from the corresponding 1,3-diaryl-2,2-dimethyl-1,3-propanediones 5, which in turn were readily available by 2,2-dimethylation of the diones 4. The acid-catalyzed cycloaddition of cyclopentadiene to the isopyrazoles 6, a Diels-Alder reaction with inverse electron demand, afforded the 1,4-diaryl-substituted gem-dimethyl azoalkanes 7 of the diazabicyco[2.2.1]hept-2-ene (DBH) type. The cycloadduct yields were strongly dependent on the nature of the aryl substituents and highest for the electron-withdrawing substituents. In acidic solution, the azoalkanes showed cycloreversion to generate an equilibrium between isopyrazole 6, cyclopentadiene, and azoalkane 7. For the p-methoxy derivative, cycloreversion was essentially quantitative, whereas only 20% cycloreversion occurred for the para nitro compound. A positive Hammett rho value (rho = 3.24 for 2 equiv of CF3COOH) was determined for the equilibrium constants of the acid-catalyzed [4(+) + 2] cycloaddition. The unsymmetrically substituted isopyrazoles gave two regioisomeric cycloadducts with a slight excess of one isomer. The direct and triplet-sensitized photochemical and thermal denitrogenation of the azoalkanes 7 gave in quantitative yields the 1,4-diaryl-substituted bicyclo[2.1.0]pentanes (BCP) 8 with retention of configuration. The azoalkanes 7 and the housanes 8 are more persistent than the related 1,4-diaryl-substituted DBH and BCP derivatives. The stabilizing effect is rationalized in terms of less favorable benzylic conjugation in the transition states for C-N (azoalkanes) and C-C (housanes) bond cleavage due to steric interactions between the geminal methyl groups at the methane bridge and the diaryl substituents at the bridgehead sites.